This research examines the interrelations of endocrine and physical growth variables and adolescents' psychological functioning. Participants are girls and boys, 9- to 14-year-olds, and their parents. Participants are evaluated on biological and psychological variables at three times of measurement, six months apart. Biological measures include stage of pubertal development, assessed by a physical examination (Tanner stages) and hormone levels, assessed by blood samples for gonadotropins, gonadal steroids, and adrenal androgens. Psychological measures include assessments of psychological and behavioral problems, cognitive functioning, self-esteem, affective states and interpersonal functioning. Assessment of parental behavior is through observations of parent-child interactions in standard laboratory situations and through standard inventories regarding childrearing attitudes and behavior. Data from the first time of testing indicate clear and consistent relationships between endocrine status and psychological functioning. For girls and boys, hormone levels indicative of a more mature endocrine status were related to feelings of low competence and negative self-image. Mothers of girls with lower levels of adrenal androgens report more anxiety, depression, withdrawal, aggression, and cruelty than mothers of girls with higher levels of adrenal androgens. Mothers of boys with the higher levels of sex steroids and adrenal androgens report more obsessive compulsive, delinquent, aggressive, hyperactive, schizoid, and uncommunicative behaviors and somatic complaints. Future analyses of the longitudinal data will examine the causal relations between changes in endocrine status and changes in psychological functioning of adolescents.